Field of the Invention
The present invention relates to a power delivery device configured for an automatic transmission. More particularly, the present invention relates to a power delivery device configured for an automatic transmission which controls a gap between friction members and provides coupling force optimized for each operating stage by selectively connecting a rotation element to a transmission housing by use of dual pistons.
Description of Related Art
Environmentally-friendly technique of vehicles is very important technique on which survival of future motor industry is dependent. As regulations of exhaust gas become tightened, vehicle makers are focusing on development of environmentally-friendly vehicles to meet environment and fuel consumption regulations.
To enhance of fuel economy, researches on high efficiency engine, high efficiency transmission, vehicle body lightening, etc. is actively proceeding. Particularly, dual clutch transmissions, automated manual transmissions, etc. having advantages of both efficiency of manual transmissions and convenience of automatic transmissions are developed briskly in a transmission field.
According to such transmissions, a rotation element is selectively connectable to and is fixed to a transmission housing by a brake of dry or wet type. Particularly, since a brake used in a dual clutch transmission and an automated manual transmission resists against engine torque directly transmitted from an engine to the brake, great coupling force and control precision are demanded.
That is, a brake for such a dual clutch transmission and an automated manual transmission is required for quick operating speed of a piston for quick power delivery at a stage (i.e., an initial operating stage) where a piston moves to a brake disk and a brake plate that are friction members and is required for great coupling force for cutting off power rather than quick operating speed of the piston after the brake disk and the brake plate are coupled.
Recently, a brake provides quick operating speed of a piston and great coupling force in the present respect, but operating speed and coupling force are not precisely controlled for each operating stage. Accordingly, operating efficiency of a brake may be deteriorated.
Furthermore, as great coupling force of the piston is repeatedly applied to the brake plate with quick operating speed, the brake may be damaged due to accumulated fatigue.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.